Process for producing nonsag tungsten wire



IP80 n3 xe 1,605,192 J33." v?- r uLrmuu Uun .p atented Nov. 2, 19 26. i I I v l UNITED STATES, PATENT OFFICE.

PAUL MOALLISTER, OF BLOOMFIEIJJ, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

V v PROCESS FOR PRODUCING- NON SAG TUNGSTEN WIRE. NoIDrawing. Application filed December 23, 1922. Serial No. 608,798.

This invention relates to incandescent edent to obtaining a good non-sag wire 55 electric lamps and, more particularly, to a' that the wire be physically homogeneous.

recess for producing a non-sag tungsten The filament should be in this condition at ament for use in such lamps. the time the lamp is first burned or else if 5 An object of the invention is to provide not present at that time it is necessary that V a process for rendering a normally non-sa such condition be developed at that time wire more resistant to sagging. and thatit be thus maintained throughout A further object of the invention is to the life of the lamp. maintain a normally non-sag lam filament I have also discovered that grain size or 1 in a condition to resist sagging toughout shape do not determine .of themselves the its normally useful life. rag-resisting qualities of a wire. Also I 65 Another object of the invention is the have discovered that it is not necessary in provision of a step in the fabrication of a :the production of a non-sag wire that any non-sag tungsten lamp filament whereby. partlcular auxiliary 1n edients or .dopin i M harmful compounds or substances within materialsbe added fit e wire. As state [the filament maybe renderedharmless to heretofore, my tests and, examinations of 70 prevent any deleterious action on the 'nonvarious so called non 'sagwire'have revealed sag properties thereof. that that quality which a wire must possess a i A still further object of the invention is in order to render the S m resistant o S gto subject a wire to the action of a strong ging isplgsical homogeneity at the timeor a reducing agent, such as arsenic or phoslmmediat y after the wire is first lighted 75 phorus, and, conjunctively therewith, in as a filament. In order that this propertytensively heating said wire, whereby delemay bepcssessed by the-wire at the time terious substances withinsaid wire may be mentioned, it is necessarythat there be rerendered harmless. moved from the wire those substances which Other objects of the invention will be apaffect the crystalline structure adversely, '8 0 parent. upon a reading of the following (1 and if the wire is introduced into a-lamp as scription. a filament, it is also a condition that any ma- Processes have been devised for obviating nal present in the lamp, which may form the tendency of coiled filaments of incanh mful compounds with the filament, be. descent electric lam s of the gas-filled t e render d rml sto elongate or sag etween su ports, w en With the end in view, therefore, of proburned at high temperatures, y producing viding a filament which is physically homea pure tungsten filament. According to geneous at the beginning of the life of the 35 these processes, it is proposed to add to the wire as a filament, I have ascertained that Wen a purifying substance, this condition may be developed by sub-co as t enitrates or carbonates of potassium jecting the wire, after its manufacture, to or sodium, silicic acid, etc. It was thought the action of a strong reducing agent, such that these processes would have the effect as arsenic, phosphorus and the like. It is'a 40 of purifying the tungsten and removing condition that the reducing agent be of such therefrom any deleterious substances which nature that it will remove moisture, oxygen may subsequentlyaflect the crystal develop: or harmful substances or compounds from ment in sald wire. the surface of the filament or within the t However, in the wire which is produced filament itself or the surrounding atmos- 4 in accordance with these processes, it is phere in which said filament may be burned.

found that there still may be included with- The reducing agent also should have a low in the wire objectionable compounds either boiling point so that it does not remain in resultin from the materials which have the w1re as an impurity. been ad ed to the wire or which said mate-f Several mcthods'may be followed in sub- 50 rials have failed to remove during the procjecting the wire to the action of the reducing ess of fabrication of the material into a wire agent. A desirable method may consist in or filament. inserting the wire into, or passing it slowly I have determined by examination of 1111- through, an enclosed vessel or tube furnace merous filaments that it is a condition precprovided with an inert environment, such as argon, nitrogen and the like. The reducing agent may be introduced into the furnace in the form of a vapor, either with or inde pendently of the inert gas. It may be desirable, however, to apply the reducing agent to the wire in the form of a coating by passing the wire through a liquid such as water containing the reducing agent in suspension. In the latter case, the reducing agent may be rendered active by heating the wire to incandescence by passing an electrical current therethrough or the wire may be heated in any other desired manner. It is preferable to heat the wire to a high temperature while the reducing agent is active as the beneficial action in removing im urities or rendering them harmless is expe ted thereby.

It may be desirable, however, from the practical and commercial .aspect to subject the wire to the reducing action after it has been inserted into the'lamp. the latter case the material which is to act as the reducing agent must be in suchcondition that its action will not be impaired. It also may be desirable that the reducing agent be active throughout the normal commercially useful life of the lamp, therefore, a suflicient quantity of the agent may be placed within the lamp toxenable' this continuous action to be maintained,'it being a condition, however, that the reducing agent employed be such that it has an appreciable vapor pressure at the lowest temperature prevailing within the lamp during operation thereof.

In order that the beneficial action of the reducing agent upon rendered more effective, it may be found as sirable to conjunctively heat the filament to a high temperature at the time the reducing agent is rendered active. To this end it may be preferable to apply thereducing agent directly to the lamp filament.

By comparison of the two sets of data hereinafter given, the reader may better appreciate the benefits derived by employ ment of my invention. Four lamps containing coils of tungsten wire made in accordance with'the standard process for producing non-sag wire, were seasoned for 15 minutes at 100% voltage and for 4.5 minutes at 115% voltage. These lamps, after. seasoning,,were tested in various ways. They showed an average bump test of 23, an average strength of coil of 10.2 and an average sag of 1.7 mm.

Another set of lamps were made up containing wire from the same spool. These lamps, however, were subjected to the action of a strong reducing agent and thereafter were tested in the same fashion as the previous lamps. T he'bump test for these lamps showed an average of 63, an average strength of coil of 21.1 and an average sag of 1 mm.

However, in

the filament may be- It is obvious from a comparison of these averages that the' lamps which were subjected to the action of a strong reducing agent showed a marked improvement over the lamps made from the same lot of wire and which were not subjected to such an agent. An examination of the micro photographs of the wire which was subjected to the strong reducing agent discloses a structure which was physically homogeneous. The wire from the other lamps, however, showed numerous 'crystal groups w 'ch interrupted and destroyed the physical continuity of the metal. Although I have specified certain materials as being desirable reducing agents, it is obvious that there are many other substances which may act in this capacity, for example, sulphur, lithium, sodium, potassium, rubidium and caesium, as well as other low-boilingpoint substances, may be employed. The best results have been obtained, however, "by employing arsenic or phosphorus. I am aware of a patent which describes the application of phosphorus to the lamp filament and the activation thereof after the lamp has been tipped-off. However, in such patent, the process claimed therein and the description relate to lamps of a diife'rent type from those which I contemplate improving, that is, such process relates to vacuum lamps; It is well known that, in a vacuum lamp,

.. effected in the properties of the filament, so

far as making the same resistant to sagging,

as the quantitiy of the ofiset-resisting material employed is so large that the reducing agent is incapable of rendering the same harmless. In lamps of the type to which my invention is applicable, the filaments are formed of tungsten to which has been added no ofi'set resisting material. In other words, the filament is formed of substantially pure tungsten. I

It is to be appreciated that departures from the invention may be obvious to those skilled in the art, however, I contemplate including such modifications as fall within the scope of the appended. claims. 1

What is claimed is: I

1. The step in the production of substantially non-sag tungsten which consists in flashing tungsten in the presence of a lowboiling point reducing agent to remove substances fromthe tungsten which affect the continuity of the tungsten structure and thereby produce a continuous tungsten strucof the non-sag type to render the same" more resistant to sagging and of greater strength, which comprises flashing 'in the presence of a reducing agent, a tungsten wire of the non-sag type to remove from said wire, substances affecting the continuity of the tungsten structure, and maintaining said continuous tungsten structure by surrounding the same with a reducing agent capable of combining with substances which would affect the continuity of the tungsten structure if combined therewith.

4. The stepin the production of substantially non-sag tungsten which consists in flashing the tungsten in phosphorus to remove substances from the tungsten which affect the continuity of the tungsten structure and thereby produce a continuous tungsten structure.

5. The step in the production of a substan tlally non-sag wire which consists in flashing, in the presence of phosphorus and the like, atungsten wire containing substances affecting the continuity of the tungsten structure to remove such substances from the wire. and thereby produce a continuous useful life of the device.

taining' said continuous tungsten structure by surrounding the same with a reducing agent capable of combining with substances which would affect the continuity of the structure if combined therewith.

7. The method of improving the non-sag and strength qualities of a tungsten wire of the normal non-sag type which comprises hermetically-sealing the same in an enclosing vessel and subjecting the wire to the action of a low boilin point reducing agent and simultaneously heating the wire, the reducing agent being in sufiicient quantity to act upon substances capable of deleteriously affectlng the wire throughout a commercially 8.. A tungsten filament substantially reslstantto sag g and of improved strength consisting o a plurality of grains or crystals of tungsten in intimate contact and having no substances between or within the grain boundaries affecting the continuity of the tungsten structure.

9. A tungsten filament substantially re-'- sistant to sagging and of improved strength comprising a substantially clean tungsten intercrystalhne structure.

10. incandescent lamp having a fi1ament therein substantially resistant to sag-- ging and of improved strength, said filament consisting of substantially clean intercrystalline tungsten free from substances affecting the continuity of the tungsten structure.

11. An incandescent lamp having a filament therein substantially resistant to sa gin throughout a commercially useful li e, sai filament .consisting of substantially clean intercrystalline tungstenfree from substances afi'ecting the continuity of the tungsten structure, and a low boiling reducing agent within said lamp capable of protecting said filament to prevent its continuity being destroyed.

In testimony whereof, I have hereunto subscribed my name this 21st day of De- 

